Wet process apparatus for making nonwoven fabrics

ABSTRACT

Apparatus for the manufacture of nonwoven fabrics on papermaking or papermaking type of machines in which fibers are deposited on an endless wire screen passing on an incline through a stock tank containing a water-fiber stock, the apparatus including an endless belt of a width substantially the same as the width of the screen in the stock tank, support elements for adjustably mounting the belt in the stock tank, a variable speed drive for the belt and adjustable rolls for adjusting the curve of the belt along the fiber-receiving face of the wire screen.

nite States Genz et al.

[ 1 Feb. 15, 1972 WET PROCESS APPARATUS FUR MAKING NONWOVEN FABRHCS Inventors: Heinz Genz, Willich; Dieter Berger; Horst Seeliger, both of Lahnstein; Karl Schmidt,

Dusseldorf, all of Germany Assignee: lFeldmuhle Aktiengesellschnft, Dusseldorf- Oberkassel, Gennany Filed: July 11, 1969 Appl. No.: 340,940

Foreign Application Priority Data July 15, 1968 Germany ..P 17 61 855.2

u.s. c1 ..162/311, 162/314, 162/317,

162/320, 162/342, 162/364 1111. c1. ..13211 1/011 field ofSearch ..162/212, 14, 16, 291, 29s,

[56] References Cited UNITED STATES PATENTS 8/1926 Klund ..162/313 6/1949 Adams..... 7/1956 Simpson... 6/1959 Muller ..162/317 X Primary Examiner-S. Leon Bashore Assistant Examiner-Thomas G. Scavone Attarney-Charles B. Smith and John A. Howson [5 7] SACT Apparatus for the manufacture of nonwoven fabrics on papermaking or papermaking type of machines in which fibers are deposited on an endless wire screen passing on an incline through a stock tank containing a water-fiber stock, the apparatus including an endless belt of a width substantially the same as the width of the screen in the stock tank, support ele ments for adjustably mounting the belt in the stock tank, a variable speed drive for the belt and adjustable rolls for adjusting the curve of the belt along the fiber-receiving face of the wire screen.

41 Claims, 2 Drawing Figures mfmmrsa 15 I972 I I 3.642.573

I00 75 50 25 O STOCK WATER REMOVAL (PERCENT) WET PROCESS APPARATUS FOR MAKING NONWOVEN FABRICS The invention relates to a device for manufacturing flat webs, such as paper, carton, and particularly nonwoven fabric,

in a paper machine the wire section of which in the region of the stock run-on is designed in the form of a steeply inclined wire and is equipped with a continuous suction box train, while the velocity'of flow of the stock water, depending on the velocity of flow through the screen, is adapted to the screen speed by devices built into the stock run-on.

It is known to use-steeply inclined wires for the manufacture of flat webs, since they permit the use of relatively long fibers, for instance synthetic fibers, in a highly dilute suspension. Nonwoven fiber fabrics in general do not appreciably resist the passage of water during dehydration and, therefore, settle very quickly on the wire section. In order to obtain a nonwoven fabric of as uniform a strength as possible in the longitudinal and transverse directions, one strives to obtain a quick deposition of the fibers on the screen, i.e., a settling of the fibers impinging on the wire in a statistically irregular (random) distribution. This is premised on a constant velocity of flow of the stock water prevailing over the entire web forming zone of the steeply inclined wire, this velocity being as identical as possible to the wire speed.

There have been attempts to solve this problem by devices built into the stock run-on. These devices consist generally of a metal sheet in the stock run-on that divides it and forms a progressively narrowing gap with the wire. This suggestion has, however, the following quite considerable disadvantages. First, each dilution of the suspension, which is known to depend on the type of fiber, particularly on its length, requires a correspondingly shaped metal sheet to be inserted into the stock run-on. This results not only in long down times, but also the difficulty, involving protracted tests, of determining for each material the optimum sheet curvature. In addition, an inventory of the various shapes of inserts is, dueto the required large quantity resulting from many different possibilities, expensive and, therefore, unecono'mical. A further particular disadvantage of the previously known fixed inserts is that the friction between the rigid insert and the rapidly flowing fiber stock suspension can cause a retardation of the suspension flow in the area of contact, leading to uniform orientation of the entrained stock fibers and the danger of vortex formation. This produces a nonwoven fabric which on the side directed towards the insert is more longitudinally oriented than it is in the cross direction, i.e., due to the vortex formation one obtains a nonuniform and faulty surface structure.

The instant invention avoids these disadvantages to produce a flat web of essentially uniform longitudinal and transverse tensile strength ratio.

The apparatus of the instant invention, used in the production of flat webs, like paper, carton, and particularly nonwoven fabric in a paper machine, in which the wire section, in the region of the web-forming zone, is steeply inclined and is equipped with a continuous suction box train, adjusts the velocity of flow of the stock water, as a function of the velocity of flow through the wire, in relation to the wire speed by means of a revolving, elastic and endless belt opposite to the wire. The elastic belt is guided in the shape ofa curve and this shape is variable.

The instant apparatus makes possible the adjustment of the web formation on the steeply inclined wire in response to variations in the stock and process conditions. In contrast to conventional Fourdrinier or cylinder paper machines, steeply inclined wires are predominantly used where one type of machine is used to produce a whole series ofdifferent kinds of materials from the thinnest tea bag paper through synthetic card papers, nonwoven clothing fabrics, to heavy mats. This requires an ability to adapt the web-forming conditions to each product and this adaptability is largely furnished by the device of the present invention. Inasmuch as the belt runs at wire speed in the direction of the wire, there is, even in the part of the stock suspension touching the belt, no braking and any orientation of the fibers is thereby avoided.

A particularly useful embodiment of the invention involves making the belt speed variable. This makes it possible to use the entire paper machine for quite different products and to operate at corresponding speeds.

Another useful embodiment of the present invention involves making the entire assembly adjustable with reference to the wire. The advantage is that, as a result, operation with stock suspensions of different dilutions, as determined by different fiber lengths and types, is feasible.

Another advantageous embodiment of the invention involves making the parts located between the belt pulleys, which determine the shape of the belt curve, adjustable. With this particular embodiment, one can obtain any arbitrary curve by an adjustment of the parts and the cost of this adjustment is negligible compared to the previous cost ofa complete replacement of a curve and in addition, the large number of fixed curves can thus be eliminated. A further advantage of this design is that, in operations with unknown or unfamiliar dilutions, it is possible to obtain the required optimum curve without any essential expense, simply by adjusting the fixtures. It has proven very useful to make these parts in the form of pulleys, because this reduces the friction between belt and part. The parts may, however, be strips of suitably curveshaped cross section arranged perpendicularly to the belt path.

A further preferred design of the device involves having the parts supported inbearings, so as to permit them to pivot about a center of rotation. The advantage of this is that the parts can be very accurately adjusted by being mounted on an eccentric shaft and they are pivoted by turning this shaft.

The adjustment of the belt which is to move with the wire is, therefore, accomplished, on one hand, by changing the distance of the entire assembly from the steeply inclined wire, and, on the other hand, by shaping the belt opposite the wire between the guide pulleys by means of curve-forming parts, so that the resulting curve is related to and is a determinant of the amount of water penetrating the screen.

In accordance with the invention, it is possible to manufacture, on one machine, products from a multitude of fiber materials and dilutions ofsuspensions without time consuming and expensive changes. Such products produced with the instant apparatus, have approximately uniform longitudinal and transverse tensile strength ratio extending over the entire cross section of the nonwoven fabric web.

Although the important advantage of the present device lies in the production of a web with essentially uniform longitudinal and transverse strength ratio, the fixture, with its manifold adjustability, makes it possible to manufacture an exactly defined product with special longitudinal-transverse strength ratio, for instance, one with an extreme ratio.

The instant invention will be more fully understood from the following description and attached drawings in which FIG. l is an elevational view, partly in section of the apparatus of the instant invention, and

FIG. 2 is a graph of the water extraction curve attained with the apparatus,

Referring to FIG. 1, endless screen wire 2 is fed, in conventional manner, around guide rolls 4, 6, through stock tank 8, across the open face of suction boxes 10, 12, 14, 16, 18, each suction box being connected by a pipe to a vacuum source, the suction in each box 10, 12, 14, l6, 18 being adjustable by a valve, not shown, in the pipe connecting the respective box to the suction source or sources. As endless screen wire 2 moves, in the direction of the arrow, FIG. 1, through stock tank 8, fibers from the water-fiber stock in the stock tank are deposited on the screen, water being withdrawn from the deposited fibers on the moving endless screen by the suction boxes as is conventional in papermaking or papermaking type machines.

In the instant apparatus, endless belt 20, which may be rubber, rubber-treated cloth as suitable belting material, and which has a width substantially equal to the width of the endless wire screen 2 in stock tank 8, passes around rolls 22,

24, 26. Roll 22 is driven, through pulley belt 28, by variablespeed motor 30 in the direction of the arrow, FIG. 1, for purposes hereinafter described.

Roll 22 is mounted on support 32 fixed to frame 34, adjustably mounted by screws 36, 38. Roll 24 is mounted on support 40 fixed to frame 34 and roll 26 is mounted on support 42 pivotally mounted in the axis of roll 24 and adjustable by screw adjuster 44 mounted on bracket 46 fixed to support 40. Tension roll 48 is mounted in slot 50 of support 52 fixed to frame 34 and is freely movable upwardly and downwardly of slot 50 to maintain constant tension on belt 20, for purposes more apparent hereinafter. Adjustable roll 54 is mounted on support 56 pivoted, at its opposite end, to support 52. Adjusting screw 58 is connected, at its end, to support 56 and is threaded, at its upper end to frame 34. By adjusting screw 58, adjustable roll 54 is adjusted changing the curve of endless belt between rolls 26, 22. Such adjustment changes the path of travel and spacing of endless belt 20 from endless screen wire 2 along the path of travel of the belt and screen wire. While only one adjustable roll 54 is shown, it is to be un derstood that additional adjustable rolls between rolls 26, 22, may be employed and that, rather than rolls, adjustable belt guides may be substituted.

In the apparatus ofthe instant invention endless screen wire 2 and belt 20 are driven in the direction of the arrows, FIG. 1. The endless belt 20 position in stock tank 2 is adjusted, by screws 36, 38, to raise or lower endless belt 20 and endless belt supporting structure and driving mechanism in the stock tank. The curve of belt 20 is adjusted by adjusting roll 54 and, where additional adjusting rolls are employed, such additional adjusting rolls. The spacing between endless wire screen 2 and belt 20 is adjusted by adjustment of roll 26 through screw adjuster 44.

Referring to H0. 2, the volume of water withdrawn from through screen 2 and the fibers deposited thereon varies from suction box to suction box, the greater volume of water being withdrawn from lowermost suction box 10, with the volume in each box thereabove decreasing. By reducing the water intake into the individual suction boxes as the deposit of the fibers on belt 2 thickens, the dehydration curve is attained. The curve shape can be controlled by the vacuum applied at each suction box and the stock velocity in tank 8 at each such suction box.

In the instant invention the stock velocity is controlled by the spacing between endless belt 20 and endless wire screen 2 by the adjustment of frame 34 and roll 26. The curve of the endless belt 20 is adjusted with adjustable roll, or rolls, 54. By adjusting the spacing, curve and speed of belt 20 relative to endless wire screen 2, the apparatus of the instant invention can be adjusted for optimum production of a wide variety of nonwoven fabric webs and a wide variety of fiber-water stocks and fibers.

The terms and expressions which have been employed are used as terms of description and not oflimitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible.

What is claimed is:

1. Apparatus for producing an endless nonwoven sheet from water-fiber stock comprising an endless wire screen; a continuous flat inclined suction box train engaging the underneath side of a portion of the screen and forming it into a flat inclined portion; the train having a plurality of suction boxes, each extending transversely across and underneath the screen and being positioned contiguously one after another upwardly along its length, each box being connected to a separately adjustable vacuum source; a stock tank having an opening at one end adjacent the inclined portion of the screen for supplying water-fiber stock to the inclined portion of the screen; means for continuously moving the screen upwardly through the stock tank and along the suction box train at a predetermined speed for depositing fibers from the stock on the inclined portion of the screen as water is drawn through it in accordance with the dlfferent vacuums m the suction boxes;

an endless elastic belt; and means positioning a portion of the belt in the stock tank a predetermined distance above the inclined screen portion, there being elements contacting but above this belt portion which form it into a predetermined curved shape adjacent the inclined-screen portion, which shape is related to and a determinant of the amount of water passing through the suction boxes to keep the velocity of flow of the stock as equal as possible to the speed of the wire along the suction box train; and means including a driven roller above the belt portion for pulling the belt upwardly in the same direction as and at the same speed as movement of the stock.

2. Apparatus according to claim 1, wherein the speed of the wire and the'speed of the belt are independently adjustable and the means for positioning the belt portion above the inclined-screen portion, includes means for raising and lowering the curved belt portion with respect to the inclined wire portion, and a means for changing the angle ofthe curved belt portion with respect to the inclined-wire portion.

3. Apparatus according to claim 2, wherein in addition there are means for adjusting the position of the elements which determine the curved shape ofthe belt portion.

4. Apparatus according to claim 3, wherein the belt curve determining elements comprise a plurality of rollers and the means for adjusting the position of each element comprises a linking member pivoted at one end to the belt portion position adjusting means and connected at its opposite end to the axis of its roller; and means for pivoting the link about its pivot point for raising and lowering the roller attached to it. 

1. Apparatus for producing an endless nonwoven sheet from waterfiber stock comprising an endless wire screen; a continuous flat inclined suction box train engaging the underneath side of a portion of the screen and forming it into a flat inclined portion; the train having a plurality of suction boxes, each extending transversely across and underneath the screen and being positioned contiguously one after another upwardly along its length, each box being connected to a separately adjustable vacuum source; a stock tank having an opening at one end adjacent the inclined portion of the screen for supplying water-fiber stock to the inclined portion of the screen; means for continuously moving the screen upwardly through the stock tank and along the suction box train at a predetermined speed for depositing fibers from the stock on the inclined portion of the screen as water is drawn through it in accordance with the different vacuums in the suction boxes; an endless elastic belt; and means positioning a portion of the belt in the stock tank a predetermined distance above the inclined screen portion, there being elements contacting but above this belt portion which form it into a predetermined curved shape adjacent the inclined-screen portion, which shape is related to and a determinant of the amount of water passing through the suction boxes to keep the velocity of flow of the stock as equal as possible to the speed of the wire along the suction box train; and means including a driven roller above the belt portion for pulling the belt upwardly in the same direction as and at the same speed as movement of the stock.
 2. Apparatus according to claim 1, wherein the speed of the wire and the speed of the belt are independently adjustable and the means for positioning the belt portion above the inclined-screen portion, includes means for raising and lowering the curved belt portion with respect to the inclined wire portion, and a means for changing the angle of the curved belt portion with respect to the inclined-wire portion.
 3. Apparatus according to claim 2, wherein in addition there are means for adjusting the position of the elements which determine the curved shape of the belt portion.
 4. Apparatus according to claim 3, wherein the belt curve determining elements comprise a plurality of rollers and the means for adjusting the position of each element comprises a linking member pivoted at one end to the belt portion position adjusting means and connected at its opposite end to the axis of its roller; and means for pivoting the link about its pivot point for raising and lowering the roller attached to it. 